This invention relates to improving the safety of the workplace, specifically in areas where people are present around large self-propelled moving equipment.
Vehicle back-up alarms have been known to promote safety on work sites for many years. When operating correctly, back-up alarms on vehicles automatically activate when the vehicle is moving in reverse. This provides a warning for those in the area where the vehicle is operating. In some applications, an automatically adjusting alarm is appropriate. An automatically adjusting alarm operates like a back-up alarm. However, instead of simply switching on the output, the unit listens to the ambient noise and adjusts its output to be merely above the prevailing noise floor.
More recently, object detection systems have found application on working vehicles. These systems constantly monitor a specific area so that detection of an object triggers a warning. This warning is typically in the cab of the vehicle and sometimes may trigger a warning outside of the vehicle.
Both the so-called listening alarm and non-listening alarm suffer from shortcomings that limit usefulness. Referring to FIG. 1, a heavy vehicle 4 is depicted while backing up with a backup alarm 12. The sound pressure level (SPL) of the alarm 12 is about 108 dB at a distance of 1 m, which then degrades according to the inverse square law to less than 93 dB at a distance of 6-8 m. However, consider a worker 2 with a jackhammer at a distance of 6 m from the backup alarm 12. Around the worker 2 is a cone of sound from the jackhammer which is at or above 96 dB measured on a 1 m radius. The worker 2 is unlikely to hear the backup alarm, thus putting the worker at risk. A non-listening alarm would not compensate for this deficiency. A listening alarm 12 would compensate for the localized noise by boosting output by about 4 dB to overcome the localized noise, but this boost is inadequate in this environment. Boosting the sound to about 88 dB at worker 2, much less than 96 dB. It is calculated that this type of alarm would have to produce a sound pressure level of 112 dB to be minimally effective.
Known patents in the field include U.S. Pat. Nos. 6,151,398; 6,678,381; 6,635,612; 6,606,389; 5,940,347; and published U.S. Application No. 2001/00043142. Known manufacturers of alarm systems which have proximity sensors include R.F. Knapp Company. Its online publicity of “DUAL DECIBEL LEVEL ALARM SYSTEMS” found at http://www.rfknappco.com/Radar_System/custom.htm (September 2004) notes an alarm system with object detection which has adjustable alarm output. The Knapp alarm is claimed to change the sound level, but no reference is made to an alternate sound template, that is, a sound pattern of a specific nature, such as a distinctive alarm sound, to provide further intelligence on the nature of the danger.
What is needed is a system that provides industry-recognized warning indications, with increased usefulness in situations of imminent danger while providing for a fail-safe operating mode.